What is the role of IHA in the diagnosis of amebiasis?

Updated: Jul 19, 2019
  • Author: Vinod K Dhawan, MD, FACP, FRCPC, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Indirect hemagglutination assay (IHA) detects antibody specific for E histolytica. The antigen used in IHA consists of a crude extract of axenically cultured organisms. Antibody titers of more than 1:256 to the 170-kd subunit of the galactose-inhibitable adherence lectin are noted in approximately 95% of patients with extraintestinal amebiasis, 70% of patients with active intestinal infection, and 10% of asymptomatic individuals.

IHA is very specific (99.1%), but it is less sensitive than ELISA. It is not useful in differentiating acute infection from previous infection, because high titers may persist for years after successful treatment. False-positive reactions at titers higher than 1:256 are rare. ELISA has replaced IHA in most laboratories. [58]


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